1. Field of the Invention
The present invention relates to an image display device that displays and erases images repeatedly while its display particles are forced to migrate in electric field.
2. Description of the Related Art
Image display devices displaying images while moving display particles in gas phase have been known. The image display devices have two substrates, at least one of which is transparent, and display particles enclosed between them in the powder form, and an image is displayed as an electric field is generated between the substrates and thus, the display particles are forced to migrate and adhere to one of the substrates. In operation of such an image display device, because an electric field is generated by application of voltage between the substrates and the display particles are forced to migrate along the electric field direction, it is possible to display and erase an image repeatedly by properly selecting the direction of the electric field.
However, these conventional devices had a problem that the display particles that have relatively large adhesive force, when adhered to the substrates, remain adhered thereto without migration, leading to deterioration in the contrast between the image and non-image regions.
For that reason, studied was treatment of the substrate surface with hexamethyldisilazane (WO2004/077140 Pamphlet). However, the device was not effective enough in lowering the adhesive force from the beginning, causing the problem of low contrast. In addition, the contrast problem was more distinctive when the image display device was used repeatedly for displaying.
Alternatively, a method of spreading particles having a very small primary particle size on the substrate surface and thus, reducing the contact area of display particles with the substrate and the adhesive force between them was disclosed (Japanese Patent-Application Laid-Open No. 2004-226768). However, such a device was also not effective enough in reducing the adhesive force sufficiently from the beginning, leading to the contrast problem. In addition, the contrast problem was more distinctive when the image display device was used repeatedly for displaying.